The present invention relates generally to transducer calibration. More particularly, it relates to a device used for calibration of a strain gage arrangement. However, it is to be appreciated that the invention has broader applications and may be advantageously adopted for use in other environments as well.
In the construction industry, it is important to know the soil characteristics of an area where a structure is to be constructed. One procedure for obtaining information on soil characteristics is achieved in conjunction with driving a pile into the soil. Such piles are driven to form building foundations. It is difficult to determine a suitable depth to which a pile must be driven, as well as to determine the number of piles necessary to sustain a desired structure.
To address these concerns, a strain transducer is attached to the pile. A strain transducer is a device which may be attached to a structure, pile, or other mechanical object undergoing stress and strain to convert variations of strain to linearly related variations in voltage. Attachment may be obtained by bolting, gluing, welding, riveting, or other means.
The strain transducer is calibrated such that outputs from the transducer signify a stress exerted by a driving force such as a driving hammer as well as the response from the soil during hammer blows. For the results of such a procedure to be reliable, the strain transducer must be accurately calibrated and the operators of the pile driving tests be aware of the characteristics of the strain transducer being used.
Since the reliability of the characteristics of the strain transducer are essential to obtaining accurate soil condition information results, industry and governments are becoming more demanding that accuracy of the strain transducers be verified. Therefore, more frequent recalibration of the strain transducers and a more precise calibration is required.
A prior art device used to calibrate strain gages and strain transducers is represented by FIG. 1. In this device, a tube 12, possibly made of steel is placed between a high pressure manual jack 14. A strain transducer 10 to be calibrated is attached to the metal tube. Thereafter, a top jack portion 16 and a bottom jack portion 18 are compressed to place pressure on the ends of the tube thereby compressing the tube 12 causing a change in output from the strain transducer 10. Readings of the strain transducer inside the calibrated steel tube are then correlated to the output of the strain transducer for development of characteristics of the strain transducer under test.
This prior art device requires a bulky, heavy-duty jack. Additionally, the precision of the strain applied to the strain transducer is difficult to measure and verify. Finally, calibration under this system is a time consuming process.
A more compact, higher precision calibrating device is desirable. Such a device should also be economical to manufacture, provide a verification of accuracy of the calibration results, and be of a sturdy overall construction. The subject invention achieves these needs and others.